Safety switch and indicating means



Oct. 9., 1 956 F. W. MURPHY EAL SAFETY SWITCH AND INDICATING MEANS Filed Dec. 2'7. 1954 MAGNE TO INVORS fly Rosalie Murphy Big, .4

ATTORNEYS United States Patent SAFETY SWITCH AND INDICATING MEANS Frank W. Murphy and Rosalie Murphy, Tulsa, Okla.

Application December 27, 1954, Serial No. 47 7,879

1 Claim. (Cl. 123-1465) This invention relates to safety devices and indicating means for internal combustion engines of the stationary type.

More specifically, the present invention is an improvement of my Patent No. 2,358,729, filed November 12, 1941, entitled Safety Switch, and is directed to the provision of means for shutting down internal combustion engines which for some cause or reason become overheated, and the provision of means which may be located remotely, if desired, from the engines for indicating the overheated condition of any particular motor.

One of the primary objects of this invention is to provide a combined safety switch and thermal indicator for an internal combustion engine which becomes operative when the engine is overheated to ground the magneto circuit, whereby the engine is rendered inoperative.

At the present time when block testing a plurality of internal combustion engines en banc or under conditions which require the operation of one or more internal com bustion engines without attendance over long periods of time, it is not infrequent that during the operation of the engines that both the oil and the water systems thereof may become extensively heated with resulting damage to the motor.

It is, therefore, another object of this invention to provide switch means for grounding the magneto circuit of an overheated internal combustion engine and to provide a visual indicator designating such an abnormal condition.

A further object of this invention is to provide in a thermo-responsive device a magnetically operated switch for grounding the magneto circuit of an internal combustion engine when the engine becomes overheated.

A still further object of this invention is to provide a switch of the type described, the switch having a snap action whereby the arcing between the switch contacts is substantially eliminated. This permits the switch to be used with engines having powerful magnetos without the arcing heat, during the closing of the switch, welding the contacts and causing them to adhere.

This invention contemplates, as a further object thereof, the provision of switch means and a visual indicator in a safety system for rendering an internal combustion engine inoperative when the same becomes overheated, whereby the operator may almost immediately ascertain the cause for the stopping of the engine and therefore proceed, without waste of time, to repair leaks, replace a broken fan belt, or to make other repairs to the engine without having to check all the possible causes for the stoppage of the engine.

Another object of this invention is to provide a device of the type described which is inexpensive to manufacture, non-complex in construction, and durable in use.

Other and further objects and advantages of the present invention will become more obvious from a consideration of the following specification when read in conjunction with the annexed drawing, in which:

Figure 1 is a front elevational view of an instrument Patented Oct. 9, 1956 panel on which are mounted a pair of safety switches and visual thermo-indicators constructed in accordance with the teachings of this invention.

Figure 2 is an enlarged cross-sectional view taken on the horizontal plane of line 2-2 of Figure 1, looking in the direction of the arrows.

Figure 3 is a schematic wiring diagram showing the safety switch and thermo device connected in the magneto circuit of an internal combustion engine.

Figure 4 is an enlarged detail view of the thermo-indicator and its associated switch contacts.

Referring now more specifically to the drawing, reference numeral 10 designates, in general, a combined thermo-indicating device and safety switch constructed in accordance with the present invention.

The combined device 10 includes a substantially circular housing 12 having a back wall 14 and a laterally projecting circumferential side wall 16. The side wall 16 is apertured at 17 and receives therethrough an elongated internally threaded collar 18 formed of any desired electrical insulating material.

An elongated externally threaded hollow tubular member 20 is threaded through the collar 18 to position an end 20a in the housing 12 while the other end 29b thereof remains exteriorly thereof. The end 20b terminates in an enlarged hollow cyclindrical boss 22 having an aperture 24 formed in the outer end wall 26 thereof.

A piston 28 is mounted for reciprocation within the boss 22, and the piston 28 is provided with an integrally formed elongated substantially cylindrical button 343 which projects through the aperture 24. An elongated rod 32 has one of its ends fixedly secured to the piston 28 and the other end thereof extends through the elongated tubular passage 201: of the hollow tubular member 20. A resilient helicoidal spring 29 is disposed within the cylindrical boss 22, the spring surrounding a portion of the rod 32 and has one of its ends abutting against the piston 28, and the other end thereof engages against the inner end wall 34 of the boss 22. The spring 29 constantly biases the piston 28 and the tubular member for movement away from each other.

An annular silver switch contact 36 is fixedly secured to the inner end of the tubular member 20 by any con ventional means, and the tubular member 20 has mounted thereon adjacent the inner end wall 34 of the boss 22 a metallic plate 38 which is held fixedly thereagainst by means of the lock washer or nut 40, the latter being threadedly mounted on the tubular member 20 as seen in Figure 2. An elongated internally threaded magnet 42 is threaded on the portion 20a of the elongated tubular member 20 for adjustment toward and away from the free end thereof to serve a purpose to be described.

Thermo-responsive means (not shown) is disposed within the casing 12 and is connected with one end of an indicating vane 44, the other end of which sweeps across a dial bearing the legends Cold, Run," and Hot. The vane 44 is formed of electric steel and has secured thereto by conventional means a silver contact 46 which is adapted for engagement, under certain conditions, with the silver contact 36 mounted on the tubular member 20. The thermo-responsive means is connected in the water system of the internal combustion engine to be controlled, and the vane 44 is grounded at G1 through wire 48. One side of the magneto 50 of the internal combustion engine is grounded at G2 for normal operation through wire 51, and the other side thereof is connected through wire 54 with the plate 38 mounted on the tubular member 20. Thus it is seen that upon the closing of the switch contacts 46 and 36, both sides of the magneto 50 will be grounded and under such conditions the internal combustion engine will be rendered inoperable.

The magnet 42 is of the permanent type and formed of such material as to provide it with a very strong magnetic field whereby upon movement of the vane 44 into that portion of the dial which indicates that the motor is running under an abnormally hot condition .the field will attract the vane 44", and snap it rapidly toward the magnet to effect engagement of the contacts 36 and 46. The snap action effectively reduces the are which may be produced between the contacts as they close and prevents the heating thereof to the point of fusion. Adjustment of the snap action is obtained by moving the magnet toward or away from the free end of the tubular member 20.

The visual indicator vane 4-4, after the switch contacts have closed, remains under the legend Hot even after the engine has fully cooled and must be reset manually. To reset the vane 44 after repairs to the engine have been made, the operator pushes the button 3% to effect lateral movement (to the left as seen in Figure 2) of the piston 28 and rod 32. The free end of the rod 32 engages the contact 46 and pushes it, together with the vane 44, away from the contact 36. The button 3% is then released to retract the rod 32, and the vane seeks and assumes its proper normal position under the force of the return spring of the thermal device.

It will be recognized that the adjustable threaded connection between the sleeve or collar 1% and the tubular member 20 provide means for adjustably positioning the contact 36, and that the magnet 42 threadedly mounted on the tubular member 29 may be selectively positioned whereby its field will influence the vane 44 at a desired point of proximation.

If desired, a pluralityof the combined safety switches and thermal indicators may be mounted on a panel board 56, as shown in Figure 1.

Having described and illustrated one embodiment of this invention in detail, it will be understood that the same is ofiered merely by way of example, and that the invention is to be limited only by the scope of the appended claim.

What is claimed is:

In an internal combustion engine having an ignition circuit, a thermal responsive indicator gauge including a vane, said vane being formed of ferrous material, means for grounding said circuit when said liquid has been heated to a predetermined temperature, said means comprising an elongated substantially hollow tubular member, means fixedly supporting said tubular member in stationary position, a switch contact fixedly mounted on one end of said tubular member, a permanent magnet mounted on said tubular member and being lon itudinally adjustable relative thereto, the other end of said tubular member having an enlarged hollow boss formed thereon, a piston mounted for reciprocation within said boss, said piston having a portion thereof extending externally of said boss, an elongated rod having an end thereof secured to said piston, a helicoidal spring disposed in said boss and surrounding a portion of said rod, said spring having an end thereof abutting against said piston and its other end engaging against a wall of said boss, a metallic plate mounted on said tubular member, means electrically connecting said plate with said ignition circuit, said vane having a switch contact mounted thereon, said vane being grounded, and said vane when moved to a predetermined position being acted upon by the magnetic field of said magnet to move rapidly said vane toward said tubular member to efiect a mechanical and electrical connection therebetwcen and thereby grounding said ignition circuit.

References Cited in the file of this patent UNITED STATES P TENTS 2,218,975 Russel Oct. 22, 1940 2,358,729 Murphy Sept. 19, 1944 2,565,312 Lamb Aug. 21, 1951 

